I misguidedly supported CND back in the day, but I'm not sure they wanted to take the law into their own hands, did they? They just thought we should get rid of our nuclear weapons, and carry on without them.
The problem with Pegida is that, however well intentioned many if not all of them may be, they do imply or arouse feeling of hate in one section of the community on account of their religion. That is something I've seen before in another part of the UK. Hopefully we would not have the scenes witnessed on the continent repeated here, where marches were accompanied by serious attacks on refugees.
This sort of thing always happens when a group of people feel that the law is not arranged in a way to deal with what they see as a perceived threat: the problem is the law is all we have. As long as they obey that and don't become a law and order issue themselves, as their counterparts in some places elsewhere have done, then I don't have a problem. There is no harm in having silent marches.